U.S. patent number 4,387,672 [Application Number 06/309,824] was granted by the patent office on 1983-06-14 for energy transfer apparatus.
Invention is credited to Alfred J. Crocker.
United States Patent |
4,387,672 |
Crocker |
June 14, 1983 |
Energy transfer apparatus
Abstract
An apparatus having cylinders arranged radially about a
rotatable shaft and a separate piston adapted to reciprocate in
each cylinder. Each piston is held in contact with a cam
eccentrically mounted on the shaft by means of linkages and
rollers. The eccentrically mounted cam produces more complete
scavenging of the cylinders and a large volume intake. The cam
profile provides greater time for the power portion of the engine
cycle than for the exhaust portion of the engine cycle. In a
four-cycle apparatus, greater time also is provided for the intake
portion of the cycle than for the compression portion of the
cycle.
Inventors: |
Crocker; Alfred J. (Toledo,
OH) |
Family
ID: |
23199815 |
Appl.
No.: |
06/309,824 |
Filed: |
October 8, 1981 |
Current U.S.
Class: |
123/54.3;
123/55.3 |
Current CPC
Class: |
F01B
9/06 (20130101); F02B 41/04 (20130101); F02B
75/222 (20130101); F01B 2009/065 (20130101); F02B
2075/025 (20130101); F02B 3/06 (20130101) |
Current International
Class: |
F01B
9/00 (20060101); F01B 9/06 (20060101); F02B
75/22 (20060101); F02B 41/00 (20060101); F02B
75/00 (20060101); F02B 41/04 (20060101); F02B
75/02 (20060101); F02B 3/00 (20060101); F02B
3/06 (20060101); F02B 075/22 () |
Field of
Search: |
;123/43C,44E,55R,55A,55AA,55SR,56R,56C |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Feinberg; Craig R.
Attorney, Agent or Firm: Wilson, Fraser, Barker &
Clemens
Claims
What is claimed is:
1. An apparatus for transferring energy, comprising:
(a) at least two cylinders;
(b) a piston reciprocably mounted within each of said
cylinders;
(c) a rotary shaft;
(d) cam means connected to said shaft for rotation therewith, said
cam means having a profile defined by a major and a minor diameter
having coincident centers, said coincident centers displaced from
the axis of said rotary shaft, said cam profile having at least two
identical profiles for reciprocating said pistons at least twice in
one revolution of said shaft;
(e) follower means following the profile of said cam means, said
follower means including at least six equally spaced rollers and
six equal length links with adjacent rollers being interconnected
by one of said links, at least two of said links being elongatable
in length and including a pair interconnected members having
overlapping portions movable relative to each other and a spring
member coupled to the overlapping portions tending to resist
elongation of said pair of interconnected members; and
(f) means connecting said pistons to said follower means whereby
one of said pistons is juxtaposed the top of its associated
cylinder by one of said identical profiles and another of said
pistons is displaced from the top of its associated cylinder by
another of said identical profiles.
2. The invention defined in claim 1 wherein the center of said
rotary shaft is displaced from the coincident centers of said cam
means along the major diameter.
3. The invention defined in claim 1 wherein pairs of said cylinders
are circumferentially spaced 180.degree. relative to each other.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention generally relates to reciprocating piston mechanisms
and more particularly to reciprocating pistons reciprocated by a
cam mounted on a rotary shaft by means of cam rollers which are
connected to the pistons.
2. Description of the Prior Art
Many energy transfer apparatuses employing cams and reciprocating
pistons have been produced in the past. Conventionally, they have
been used in internal combustion engines, compressors, and the
like.
For example, one type of reciprocating piston internal combustion
engine employing cams for operating pistons, is illustrated in the
United States Pat. No. 1,765,713. As disclosed therein, cylinders
are arranged radially about a drive shaft. Each piston within a
cylinder is attached to a roller which is held in contact with a
first cam mounted on the drive shaft. Linkages and a second set of
rollers riding on a second cam on the drive shaft hold the rollers
attached to the pistons in contact with the first cam so that as
the pistons reciprocate, the cam is caused to rotate to in turn
rotate the drive shaft. In order to maintain the rollers attached
to the piston in contact with the cam, the second cam has a
different profile from the first cam. A modification of this type
of engine is illustrated in U.S. Pat. No. 1,863,877 in which a
spring loaded strap extends over sets of rollers to hold the
rollers attached to the pistons in contact with the cam. The cam
illustrated in this patent has major and minor diameters which are
displaced from one another by less than 90.degree. so that the
power and intake strokes of the piston occur over 35.degree. of
shaft rotation and the compression and exhaust strokes of the
pistons occur over 55.degree. of shaft rotation. In the
above-described arrangements, the center of the cam is coincident
with the center of the drive shaft. Accordingly these arrangements
appear to provide less efficiency over conventional engines having
a crank shaft for converting reciprocating motion to rotary motion
since intake and power portions of the cycle take place over a
smaller percentage of the total cycle than the compression and
exhaust portions of the cycle. Furthermore, a complicated
arrangement is required for holding the piston mounted rollers in
contact with the cam.
SUMMARY OF THE INVENTION
According to the present invention, an improved, more efficient
energy transfer apparatus is provided of the type including at
least one cylinder radially arranged about a rotatable shaft. The
cylinder has a reciprocating piston which is attached either
directly or through a connecting rod to a roller. The piston
connected roller is held in contact with a cam mounted on the drive
shaft by means of six equal linkages and rollers which engage the
cam. The cam is symmetrical in cross-section in that all diameters
have coincident centers and, in accordance with the invention, the
centers are displaced from the axis of the rotatable shaft along
the major diameter of the cam. This construction produces a
complete scavenging of the cylinder during the pistons exhaust
stroke and a larger cylinder volume on the pistons intake stroke.
Further, the cam is designed with a major diameter and a minor
diameter which are displaced from one another by other than
90.degree. so that, in the case of an internal combustion engine,
the intake and power strokes of the engine, for a four cycle
engine, take place over greater than 90.degree. of shaft rotation
and the compression and exhaust strokes take place in less than
90.degree. of shaft rotation to provide greater efficiency in the
engine, particularly when the engine is operated at higher speeds
with relatively slow burning fuels.
Accordingly, it is an object of the invention to provide an
improved, efficient energy transfer apparatus wherein the cylinders
are completely scavaged and an incoming charge is large in
volume.
Another object of the invention is to produce an energy transfer
apparatus with a long intake stroke.
Still another object of the invention is to produce a four cycle
energy transfer apparatus with intake and power strokes longer in
duration than compression and exhaust strokes.
BRIEF DESCRIPTION OF THE DRAWINGS
The above-mentioned and other features, objects and advantages and
a manner of obtaining them are described more specifically below by
reference to an embodiment of the invention shown in the
accompanying drawings, in which:
FIG. 1 is a fragmentary diagrammatic view of an energy transfer
apparatus constructed in accordance with an embodiment of the
invention and showing the cam profile, the linkages and the rollers
for converting reciprocating motion to rotary motion;
FIG. 2 is a cross-sectional view through a reciprocating piston
energy transfer apparatus illustrated in FIG. 1;
FIG. 3 is a graph illustrating an exemplary cycle of the apparatus
of the present invention;
FIG. 4 is a side view of an expansion link for use in the apparatus
of the present invention; and
FIG. 5 is a bottom view of the link illustrated in FIG. 4.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Although the energy transfer apparatus constructed in accordance
with the present invention, will be described in conjunction with a
reciprocating piston, internal combustion engine, it should be
understood that it is adaptable for use in other types of
apparatus, such as compressors and the like.
Referring now to the drawings and particularly to FIGS. 1 and 2, an
energy transfer apparatus 10 is illustrated in conjunction with a
reciprocating piston internal combustion engine 10a. The engine 10a
generally includes a drive shaft 11 to which a cam 12 constituting
a portion of the energy transfer apparatus 10 is attached by means
of a key 13. The shaft 11 and attached cam 12 rotate on a plurality
of bearings 14. The engine 10a preferably includes at least two
cylinders 15 and 15a extending radially outwardly from the shaft
11. Each piston 16 and 16a is positioned in the cylinders 15 and
15a, respectively, for reciprocation towards and away from the
shaft 11. Each piston 16 and 16a is connected through a pin 17 and
17a to a roller 18 and 18a, respectively, which ride on the cam 12.
For a four cycle engine, as the shaft 11 and cam 12 rotate, the cam
12 forces the pistons 16 and 16a outwardly away from the shaft 11
during compression and exhaust strokes and pulls the pistons 16 and
16a radially inwardly towards the shaft 11 during the intake
stroke. In an internal combustion engine the pistons 16 and 16a
apply power to rotate the cam 12 during the power stroke. However,
in a compressor the cam 12 drives the pistons for causing them to
deliver compressed charges of gas, such as air from the
cylinders.
The engine 10a may be provided with any suitable conventional value
arrangement for supplying an air/fuel mixture to the cylinders 15
and 15a during the intake stroke of the pistons 16 and 16a. In the
exemplary engine 10a illustrated in FIG. 2, two cams 19 and 20 are
provided for operating valves 21 and 22, respectively, for
supplying an air/fuel mixture to or exhausting gases from the two
cylinders 15 and 15a. Of course, the engine 10a may be of other
designs, such as a diesel engine, in which fuel is injected
directly into the cylinder.
Turning now to FIG. 1, a diagrammatic fragmentary portion of the
engine 10a illustrates the shape and operation of the cam 12 for
rotating the shaft 11 and moving the pistons 16 and 16a. The upper
one of the pistons 16 is shown attached to the roller 18 which
rides on the cam 12 and the lower piston 16a is shown attached to a
roller 18a which also rides on the cam 12. The linkages 25 through
30 are each of identical length and adjacent ones of the linkages
25 through 30 are pivotally connected together. The adjacent
linkages 25 and 26 are connected together and pivotally attach to
an idler roller 31 which rides on the cam 12. Similarly, the
adjacent linkages 26 and 27 are pivotally connected together and
are connected to an idler roller 32 which rides on the cam 12. The
adjacent linkages 28 and 29 are pivotally connected together and
are connected to an idler roller 33 which rides on the cam 12 and
the adjacent linkages 29 and 30 are pivotally connected together
and are connected to an idler roller 34 which rides on the cam 12.
The adjacent linkages 25 and 30 are pivotally connected together
and are connected to the roller 18 which in turn is connected to
the piston 16 and the adjacent linkages 27 and 28 are pivotally
connected together and are connected to the roller 18a which is
connected to the other piston 16a. The cam 12 is designed in
combination with the linkages 25 through 30 so that, as the cam 12
rotates, each of the rollers 18, 18a and 31 through 34 stay in
contact with the cam 12.
The design of the cam 12 is best illustrated by referring to both
FIGS. 1 and 3. The center of the cam 12 is off-set from the axis 35
of rotation of the shaft 11 along the major diameter of the cam. In
other words, the axis 35 of rotation of the shaft 11 is positioned
along the line of the major diameter of the cam 12 at a desired
spacing from the center 12a. This arrangement alters the
displacement of the pistons 16 and 16a in the cylinders 15 and 15a,
respectively. It will be noted that in this arrangement, the cam 12
is eccentrically mounted on the shaft 11 and must be dynamically
balanced for high velocity operation. The cam pattern is provided
with a major diameter which is a maximum distance between the axes
of any two opposed rollers, such as between the two rollers 18 and
18a, as the cam 12 rotates. The cam 12 also has a minor diameter
which is a minimum distance between the axes of the two opposed
rollers 32 and 34, as illustrated in FIG. 1. The major diameter has
a radius length A and the minor diameter has a radius length B, as
labelled in FIG. 1. The stroke of each piston 16 and 16a is the
difference between the major and minor radii A and B. Accordingly,
by displacing the center 12a of the cam 12 from the axis 35 of
rotation for the shaft 11, the displacement of the pistons 16 and
16a in the cylinders 15 and 15a is altered so as to cause the
piston 16 to completely scavenge the cylinder 16 in the exhaust
stroke. It will be noted in FIG. 3 that the piston 16a causes a
larger fuel/air mixture to be drawn into the cylinder 15a during
the intake stroke and adequately compressed during the compression
stroke.
The major and minor radii A and B are displaced from one another by
an angle other than 90.degree.. This displacement is in a direction
to provide greater time for the intake and power strokes for a four
cycle engine than is provided for the compression and exhaust
strokes. For example, in the illustrated cam 12, the major and
minor radii are spaced apart to provide 120.degree. of shaft
rotation for the intake stroke, 60.degree. of shaft rotation for
the compression stroke, 120.degree. of shaft rotation for the power
stroke and 60.degree. of shaft rotation for the exhaust stroke.
This arrangement provides greater efficiency in the engine,
particularly at higher engine speeds with relatively slowly burning
fuels.
In a reciprocating piston engine, a valve is opened during the
intake portion of the cycle and fresh air or an air/fuel mixture is
drawn in to the cylinder as the piston moves downwardly in the
cylinder. In non-supercharged engines, there is a relatively low
pressure differential causing the fresh air or air/fuel mixture to
flow into the cylinder during the intake portion of the cycle. By
providing a greater time for this portion of the cycle, the engine
is more efficiently charged with fresh air or with an air/fuel
mixture. This is particularly true at higher engine speeds where
very little time is provided for intake. A greater time also is
provided during the power portion of the cycle. This greater time
interval allows for a release of working pressure over a wider
angle of shaft rotation. Furthermore, the additional time for the
power portion of the cycle results in a greater pressure on the
piston at the end of the power stroke since there is more time for
completion of combustion. On the other hand, the time required for
the compression and exhaust portion of the cycle is not critical
and, by shortening the time for these portions of the cycle,
additional time is provided for the intake and power portions of
the cycle.
The design of the cam 12 is best illustrated in FIG. 1 and the
graph in FIG. 3. In FIG. 3, a line 41 illustrates the position of
the piston as the shaft 11 and cam 12 rotate through 120.degree.
for the intake stroke, through 60.degree. for the compression
stroke, through 120.degree. for the power stroke and finally
through 60.degree. for the exhaust stroke of the piston. It should
be noted that during the power stroke, the piston initially moves
very little to allow pressure buildup which is finally released
over the latter part of the stroke. The actual curve for the power
stroke is selected to provide desired operating characteristics to
the engine.
In designing the pattern for the cam 12, the initial step is to
determine a desired displacement for the reciprocating pistons 16
and 16a. From this selected displacement, the major radius A and
the minor radius B are selected. Several points, points 42 through
44, on the line 41 representing the desired position of the piston
versus angular rotation of the cam 12 are marked on the line 41 of
the graph of FIG. 3. These points 42 through 44 are used for
generating a cam pattern 45 (See FIG. 1) for a portion of the
cycle, such as for the illustrated intake portion of the cycle. An
actual cam profile 46 is formed from the cam pattern 45 by allowing
for the radius of the rollers 18, 18a, and 31 through 34. In other
words, the cam profile 46 corresponds to the cam pattern 45, only
smaller by the radius of the rollers 18, 18a and 31 through 34.
The links 25 through 30 are established at a uniform length
normally equal to a line interconnecting the major and minor radii
A and B only spaced apart by 60.degree. about the center 12a of the
cam 12. The link 30 in FIG. 1, for example, illustrates this since
it has pivot connections on its opposite ends lying on a circle
formed about the center 12a of the cam 12 having the radius A of
the major diameter and lying on a circle having the radius B of the
minor diameter for the cam 12.
After the portion of the cam profile 46 for the intake stroke is
established, the power portion of the stroke preferably is made
identical so that each diameter of this portion of the cam has a
midpoint coincident with the cam 12. The compression and exhaust
portions of the cycle are generated by the rollers 32 and 34 as the
cam 12 rotates and the rollers 18, 31 and 33 move over the power
and intake curves of the cam 12. By thus generating the cam profile
for the compression and exhaust portions of the engine cycle, the
rollers 18, 18a and 31 through 34 will all maintain contact with
the cam 1 as the cam 12 is rotated through 360.degree..
When a cold engine is initially started and has not reached its
normal operating temperature, the cam 12 and the linkages 25
through 30 may be subjected to thermal stresses for a short period
of time which temporarily produce non-uniform thermal expansion of
the cam 12 and/or of the linkages 25 through 30. If desired, either
all of the links or the two opposed links such as the links 26 and
29, may be replaced with expandable links, such as the link 50
illustrated in FIGS. 4 and 5. When the link 50 replaces the link
29, for example, it has an end 51 connected by a pivot pin 52 to
the roller 33 and also to the adjoining link 28 and 34 and to the
adjoining link 30. The link 50 includes two similar, parallelly
arranged expansion side members 59 and 60, each comprising an
inside member 61 and an overlapping end portion, outside member 62,
the overlapping ends being suitably interconnected by a tension
spring 63 which resiliently prevents and limits elongation. As
forces are exerted on the pins 52 and 56 tending to elongate the
link 50, the ends of the overlapping portions of each member 61 and
62 of each side 59 and 60 move toward each other, as illustrated by
arrows in FIG. 5, allowing the rollers 33 and 34 to move apart
slightly. Thus, the link 50 will maintain the rollers in contact
with the cam 12 even though there is non-uniform thermal expansion
during initial warm-up of the engine. An expandable link, such as
link 50, also may be used for taking up slack as the cam and the
rollers wear during extended use of the engine.
As stated above, the six links are selected to extend between
circles formed by the major and minor radii over a 60.degree.
segment about the center of rotation of the cam. The cam profile is
selected for one portion of the operating cycle of the engine, such
as the power portion, and the profile is generated by the rollers
for the next portion of the cycle, such as the exhaust portion. The
generated cycles may be modified slightly by making slight, equal
adjustments in the length of the links 25 through 30. In each case,
the portion of the cycle which is generated is selected to maintain
the rollers in contact with the cam surface. In establishing the
size of the cam during the initial design, the stroke, which is the
differences between the major and minor radii, normally cannot
exceed the minor radius, unless the length of the links are
shortened. If the stroke does exceed the minor radius and the links
are not shortened, two adjacent links will approach a straight line
at times during the cycle and an unstable condition may result with
the rollers moving out of contact with the cam. In some cases, the
stroke may be selected to equal the minor radius. An unstable
condition can be eliminated by slightly decreasing the lengths of
the link which will in turn modify the generated portion of the cam
pattern.
The above-described energy transfer apparatus 10 has several
benefits over prior reciprocating piston mechanisms. By increasing
the length and duration of the intake stroke, the volumetric
efficiency is increased due to the greater volume and proportional
time for intake and by quickly compressing the charge there is less
chance for pre-ignition, spark knock, reduced thermal losses to the
cylinder walls and etc. By increasing the duration of the working
or power stroke, the working pressure is released over a wider
angle of shaft rotation and a higher pressure is maintained over a
greater portion of the power stroke. Furthermore, the piston
velocity and the piston ring seal velocity is at a minimum when the
pressure on the piston is the highest. Finally, the design allows
for varying and selecting a desired movement of the piston in
portions of the operating cycle of the engine. Still another
advantage over engines of the type having a crank shaft is that the
shaft 11 of the engine 10 turns at one-half the normal speed of a
conventional engine shaft, thereby reducing wear on the engine.
Furthermore, a more complete combustion of the fuel/air mixture and
better scavenging of the cylinder is obtained.
It will be appreciated that various modifications and changes may
be made in the above-described energy transfer apparatus 10 without
departing from the spirit and scope of the invention. For example,
the invention has been described as being embodied in a four cycle
engine. The invention is equally applicable to a two cycle engine.
The energy transfer apparatus 10 has been described as completely
scavaging the cylinders on the exhaust stroke and as having
120.degree. of shaft rotation for the intake and power strokes and
60.degree. of shaft rotation for the compression and exhaust
strokes. The cam may be offset for other piston displacements and
modified for other shaft rotations, such as 115.degree. rotation
for the intake and power strokes and 65.degree. rotation for the
compression and exhaust strokes. Generally, it does not appear to
be desirable to exceed about 135.degree. of shaft rotation for the
intake and power strokes. However, in accordance with the present
invention, the power stroke will take place over greater than
90.degree. of shaft rotation to provide an increased efficiency
over prior art crank shaft type engines.
The apparatus 10 has been described as having a single cam for
moving the pistons 16 and 16a. It should be appreciated that
additional pistons may be mounted about the cam such as three
pistons or six pistons, and that additional cams may be mounted on
the shaft 11 for driving additional pistons. Furthermore, it should
be noted that the single cam 12 may be replaced with three cams
spaced along the shaft 11 with the two outer ones of the cams
identical and keyed to the shaft 11 and the inner one of the cams
gear driven in the opposite direction so that the three cams
simultaneously engage the piston rollers 18 and 18a for
reciprocating the pistons 16 and 16a. With this arrangement, no
side loading forces are exerted on the pistons 16 and 16a or their
connecting rods. As far as the linkages are concerned, an apparatus
in accordance with the present invention must have at least six
linkages in order to maintain proper contact between the rollers
and the cam. A greater number of linkages may be provided if
desired. However, the stroke of the engine must be reduced or the
minor diameter must be increased when more than six linkages are
used to prevent adjacent linkages from approaching an unstable
straight line during rotation of the cam.
In accordance with the provisions of the patent statutes, the
principles and mode of use of the invention has been explained and
what is considered to represent its preferred embodiment has been
illustrated and described. It should, however, be understood that
the invention may be practiced otherwise than as specifically
illustrated and described without departing from its spirit and
scope.
* * * * *